The present invention relates generally to a multi switched network system (IP communication network system) capable of reducing costs for equipment and operations by integrating a switched circuit network such as a telephone network with an IP (Internet Protocol) packet switched network such as the Internet or the Intranet, and more particularly to an IP communication interface device and a circuit switch for facilitating a construction of this IP communication network system.
With an advancement of a network technology as typified by broadening the band of a local area network (LAN) and an advancement of a PC technology as typified by attaining multifunctions of a personal computer (PC) and a speed-up of a CPU applied to the PC over the recent years, it is on the verge of actualization in terms of utilization that voice data are communicated at a high speed between the PCs on a plurality of LANs.
Owing to the advancements of those technologies, application software executed between the PCs on the Internet (including the Intranet as far as it is not used in a particularly limited terminology in this Specification) configured by the LANs and wide area networks (WANs) and a hardware system incorporating this package software, are rapidly put into the market. This system is known as [Internet telephony].
In the IP communication network system known as Internet telephony, an integration of the data communications with the voice communications involves the use of a VoIP (Voice over Internet Protocol) technology. This VoIP technology is that voices (audio data) are segmented into frames at an interval of a short time (on the order of, e.g., 20 sec), and transmitted and received in the form of packets by adding IP headers thereto on a network (IP network) based on a network layer protocol, i.e., Internet Protocol (IP) used on the Internet.
Further, there is promoted a development of an interface device, incorporating a gateway function for executing a communication protocol conversion between the telephone network and the Internet, for actualizing the communications between the telephone network and the Internet.
Generally, the Internet telephony can be operated at a lower cost than a speech (voice communication) on the phone through the conventional telephone network, and therefore a spread of the IP communication network system and services thereof is being accelerated.
A transmission (transfer) standard in this IP communication network system is not yet, however, established. What exists at the present is just ITU-T Recommendation H.450.2 (H.323) that defines the services within the Internet and the services in the conventional telephone network.
With diversification and a scale-up of the infrastructures for the communications, the users tend to separately use the communication infrastructure optimal to the purpose. Under such circumstances, it is necessary and indispensable to construct a more economical intra-office communication network system by taking the Internet into the intra-office communication network system and utilizing it for the data communications and the voice communications as well.